1) I am interested in outputting environmental variables after setting them in a rewrite, for example:

%{FOOBAR}e

From apache:
"%...{FOOBAR}e The contents of the environment variable FOOBAR"

I can never get the variable output in the log though I can confirm it is set in the environment.

2) I also wish to use the < > modifiers with %U

%>U and %<U

From apache:
"The modifiers "<" and ">" can be used for requests that have been internally redirected to choose whether the original or final (respectively) request should be consulted. By default, the % directives %s, %U"